1. Field of the Invention
The present invention relates to a double rotation type scroll expander in which a drive scroll body and a driven scroll body rotate synchronously.
2. Description of the Related Art
Conventional power generation systems tend mostly to be large scale plants generating at least several hundred kW, while small scale power generation is performed mostly by simply structured engine power generators and the like. Recently, however, due to increased awareness of the need for energy conservation, passage of the Act on Special Measures Concerning Procurement of Renewable Electric Energy by Operators of Electric Utilities, and the like, a need and a market for small scale power generation are gradually increasing. Photovoltaic generation and wind force power generation, on the other hand, have not yet improved in cost-effectiveness. Meanwhile, a binary power generation system that uses hot water or steam at 75 to 150° C. as a heat source to drive a small scale power generator via a working medium having a low boiling point has been developed.
Amid these developments, a scroll expander, which obtains rotary torque for a drive shaft by supplying a high-pressure working medium to an expansion chamber, has come to attract of attention as a favorable expander for use in a small scale power generation system due to the fact that a scroll expander exhibits little torque variation. In a scroll type fluid machine, a compression chamber and an expansion chamber are formed by end plates and spiral-shaped wraps of a pair of scroll bodies. Japanese Patent Application Publication No. 2009-299653 discloses a one-side revolving type scroll expander in which one of the pair of scroll bodies is a fixed scroll body and the other is a revolving scroll body, and the expansion chamber is formed by causing the revolving scroll body to revolve relative to the fixed scroll body. A scroll type fluid machine thus configured is dynamically sealed, and therefore noise and wear tend to increase in contact sites with the end plates and the wraps forming the expansion chamber, whereby a sealing property of the expansion chamber may be impaired.
Japanese Patent Application Publication No. 1-16-341381 discloses a double rotation type scroll fluid machine. In a double rotation type scroll fluid machine, a drive scroll body and a driven scroll body are rotated synchronously via an interlocking mechanism, and therefore noise and wear in the contact sites can be reduced. In the double rotation type scroll fluid machine, the compression chamber and the expansion chamber are formed by causing the driven scroll body to rotate eccentrically relative to the drive scroll body.
The double rotation type scroll fluid machine disclosed in Japanese Patent Application Publication No. H6-341381 has a so-called “double wrap scroll structure” in which the compression chamber or the expansion chamber is formed on both surface sides of the end plate of the driven scroll body. By forming the compression chamber or the expansion chamber on both sides in this manner, a processing capacity and an output (a rotary torque) of the working medium can be increased. Further, a thrust direction load exerted on the drive scroll body and the driven scroll body can be canceled out, and therefore a support structure for the drive scroll body and the driven scroll body can be simplified.
In a double rotation type scroll expander, however, the drive scroll body and the driven scroll body are caused to rotate synchronously, and therefore a double rotation type scroll expander requires a greater driving force than a one-side revolving type scroll expander. Hence, to obtain a high output, the working medium must be supplied to the expansion chamber while preventing leakage of the working medium and pre-expansion due to a temperature reduction before the working medium is supplied to the expansion chamber. With the double rotation type, however, it is more difficult to secure a working medium supply passage that satisfies both of these conditions than with the one-side revolving type.
In the double rotation type scroll fluid machine disclosed in Japanese Patent Application Publication No. H6-341381, a drive shaft is divided into two in an axial direction, whereby a problem arises in that alignment of the axial centers of the two divided drive shafts is troublesome. Further, when the double rotation type scroll fluid machine is used as a scroll expander, the high-pressure working medium is first supplied to one expansion chamber through a high-pressure fluid introduction hole provided in one of the divided drive shafts, and then supplied to the other expansion chamber through a hole provided in a partition wall between the expansion chambers. Hence, a problem arises in that pressure loss occurs in the working medium while passing through the hole, with the result that the working medium is not supplied evenly to the two expansion chambers. Further, the driven scroll body includes a housing that covers an expansion chamber formation region, and therefore a weight of the driven scroll body increases, whereby a greater driving force is required to rotate the driven scroll body.